Manufacture of hydrazine



July 6, 1954 R- S. PRATT MANUFACTURE OF HYDRAZINE Filed April 26, 1950 l3 PHOTOCHEMICAL RADIATION l I Q ACTIVATION ZONE DIMER FORMATION ZONE HYDROGENATION ZONE REACTOR HEXANE DRAW-OFF HYDRAZINE PRODUCT TO PUR'IFI CATION INVENTOR ROBERT S. PRATT BY J" ATTORNEYS Patented July 6, 1954 UNITED STATEZ FATENT OFFICE MANUFACTURE OF HYDRAZINE Application April 26, 1950, Serial No. 158,121

18 Claims. 1

This invention relates to the manufacture of hydrazine. In one aspect the invention relates to a process for the manufacture of hydrazine from activated hydrocarbons. An object of the invention is to provide an efficient process for the manufacture of hydrazine. Another object of the invention is to provide an eflicient process for the manufacture of hydrazine from readily available materials. Other objects and advantages inherent in the invention will become apparent from the following disclosure.

According to this invention, the manufacture of hydrazine is accomplished, generally, by reacting an agent, capable upon activation of producing an alkyl radical having not more than two carbon atoms, with an oxide of nitrogen to produce a dimer of a nitrosoalkane. This dimer is next hydrogenated under suitable operating conditions to produce a mixture comprising hydrazine and an alkane. Hydrazine is then separated from the mixture obtained by the above hydrogenation, as a product of the process. The term hydrazine is employed for the sake of convenience, but is intended to include not only hydrazin itself, but also hydrazine hydrate.

The agent employed for producing the nitrosoalkane dimer is preferably selected from the group consisting of methane, ethane, metal derivatives of methane or ethane, ethylene oxide or propylene oxide. The term agent as used throughout this description is intended to include any of the aforementioned compounds. Suitable metal derivatives are tetramethyl lead, tetraethyl lead, dimethyl zinc, diethyl zinc, dimethyl mercury and diethyl mercury, The oxide of nitrogen employed for the above nitration of the agent is preferably nitric oxide or nitrogen trioxide.

As indicated above the agent is employed in a suitably activated condition. Such activation may be obtained either by photochemical or thermal decomposition, which enables the agent to give up its alkyl radical (i. e., either the methyl or ethyl radical, depending upon the structure of the agent) for reaction with the oxide of nitrogen (either nitric oxide or nitrogen trioxide) to produce a dimer of a nitrosoalkane. The decomposition of the agent and reaction of the freed alkyl radical with the oxide of nitrogen to form the dimer, may be represented by the following equations in which methane is employed as a suitable agent, nitric oxide is employed as a suitable oxide of nitrogen and hi represents the energy required for suitable activation.

It will be noted that where the agent is either methane, ethane or their metal derivatives, activatlon thereof and subsequent reaction with the oxide of nitrogen will produce the dimer of the corresponding nitrosoalkane. However, where the agent is ethylene oxide, activation produces a methyl radical so that the dimer of nitrosomethane is formed upon subsequent reaction with the oxide of nitrogen. Similarly, propylene oxide upon activation and subsequent reaction with the oxide of nitrogen will produce the dimer of nitrosoethane.

As indicated above, the activation of the agent to free the alkyl radical is carried out either by photochemical or thermal decomposition. When carrying out the activation photochemically, suitable activation media are employed such as direct sunlight or ultra-violet radiation produced by electrical energy (for example, lamps capable of producing ultra-violet light). Apparatus employed for carrying out the photochemical decomposition conveniently comprises a vertical elongated tube, made of quartz or suitable metal Or metal alloys, through the upper end of which the agent is introduced. At an intermediate point along the tube, ultra-violet light from a suitable source of radiation is introduced through a transparent window. This window is made of a suitable material which will not prevent the transmission of ultra-violet light such as quartz or glass with a capacity for high ultra-violet ray transmission, so that the passage of the agent past the point of introduction of ultra-violet light will cause activation of the agent and effect the freeing of the alkyl radical by photochemical decomposition, as indicated by Equation I above.

To effect reaction between the oxide of nitrogen, i. e., either nitric oxide or nitrogen trioxide, and the free alkyl radical of the activated agent in forming the desired dimer, the oxide of nitrogen is introduced into the tube preferably at a point below the point of introduction of ultraviolet radiation. It is preferred, however, to introduce the oxide of nitrogen into the tube at a point as close to the point of origin of the freed alkyl radical, preferably without subjecting the oxide of nitrogen to the action of ultra-violet radiation, in order to increase the yield of the resulting dimer. The quantit of the oxide of ntirogen thus introduced into the tube is at least in stoichiometric proportions and not more than an excess of about 20%, in accordance with the Equation II above. The above activation and reaction to produce the dimer is preferably carried out at atmospheric or slightly reduced pressure (for example, between about 500-760 mm.

of mercury, although pressure as low as 1 mm. of mercury may also be employed) and preferabl with a catalytic agent such as mercury vapor. Suitable temperatures to be maintained in the tube during activation of the agent and subsequent dimer formation are between about 0 C. and about 122.5" C., with a temperature between about 20 C. and about 20 C. being preferred. Th dimer of the selected agent will form at a temperature of about l22.5 C. or below, depending upon the characteristics of the particular agent selected. However, if the temperature within the tube is maintained above approximatel 122.5 C., the monomer will form and is obtained as a liquid. Upon subsequent cooling to a temperature of about 122.5 C. or below, the monomer will be converted to the desired dimer, and will be obtained. as a solid. It will be noted that it i not essential that such conditions be maintained within the tube as will in all cases cause the solid dimer to be formed. While it is preferred to obtain and. withdraw the solid dimer directly, as an intermediate product of the process, it is also satisfactory to form the monomer, if so desired, and withdraw it as a liquid which upon subsequent cooling will form the dimer for further treatment in accordance with the process hereinafter described.

In maintaining the desired temperature conditions within the tube, suitable heating or cooling means may be employed such as heat exchange coils wound around the reaction tube. If desired, it is also possible to preheat or cool the agent and/or the oxide of nitrogen prior to introduction into the tube. When the agent employed is ethylene oxide (liquid) or propylene oxide or a metal derivative (for example, tetramethyl lead), it will be present either as a liquid or as a solid (for example, dimethyl zinc), rather than as a gas. In such instances it is desirable to introduce these compounds into the tube through a suitable fine-mesh screen for solids, or a. spray-valve for liquids, positioned in the tube near the point of introduction, to break up the liquid or solid metal compound into fine particles for subsequent ease of decomposition and thus facilitate the desired dimer formation. It is also possible when employing the agent as a metal derivative to activate it, either by photochemical or thermal decomposition, in a suitable heating vessel such as a distillation flask, to free the alkyl radical. The alkyl radical thus freed is obtained in the form of a gas and may then be introduced into the aforementioned quartz tube, by suitable pumping means, for reaction with the oxide of nitrogen, as previously described, and

thus form the desired dimer.

As indicated above, the activation of the agent to free the alkyl radical may also be carried out by thermal decomposition. Thermal decomposition is preferred where the agent is present in the form of one of the aforementioned metal derivatives, while photochemical decomposition is preferred where the agent is in the form of a gas such as methane or ethane. In carrying out the decomposition of the agent or a metal derivative, apparatus similar to that employed for photochemical decomposition may be employed to activate the starting material. Similar broad and narrow temperature and pressure ranges are employed in activating the agent thermally when the agent is present in the form of one of the aforementioned metal derivatives, as were employed in photochemical activation or decomposition. However, higher temperatures are required when employing thermal activation of the agent in the form of methane or ethane in order to increase the yield of the resulting dimer. Such temperatures are preferably between about 100 C. and about ll00 C. The thermal activation of the agent, such as methane, ethane or ethylene oxide ma be carried with or without the presence of a suitable metallic hydrogen acceptor. Such hydrogen acceptor may be palladium or platinum. Thermal activation of the metal derivative, is preferably carried out without the presence of a hydrogen acceptor.

As previously described, the dimer produced by the above reaction between the oxide of nitrogen and the activated agent is obtained as a solid. It will be noted from Equation I, above, that as a result of the activation treatment molecular hydrogen is formed in addition to any other products of decomposition, such as free metals. However, if an excess of the oxide of nitrogen is employed in carrying out reaction with the alkyl radical (Equation 11), water instead of molecular hydrogen will be present. In the latter instance the dimer will be obtained in the form of a suspension rather than as a pure solid. The dimer thus obtained, either as a solid or as a suspension, is next hydrogenated under suitable operating conditions to produce a mix ture comprising hydrazine and a gaseous alkane derived from the starting material employed in the initial reaction step. This hydrogenation of the dimer may be represented by the following equation:

In carrying out the hydrogenation treatment of the dimer to produce the desired hydrazine product, the hydrogenation may be carried out in a suitable vessel, such as a reactor. The hydrogenation treatment is preferably conducted with the dimer present as a suspension. Suitable vehicles for forming the suspension are water, methyl and ethyl alcohol, acetone, carbon tetrachloride, chloroform ether, benzene or higher alkanes such as pentane, hexane or heptane. Where the dimer is already obtained as a suspension or slurry immediately following formation after treatment of the aforementioned free radical with the oxide or" nitrogen, additional water may be added if necessary to bring the dimer in suspensi n into a sufficiently finely divided state. The vehicle ma be admixed with the dimer previously Withdrawn from the quartz tube and the resulting mixture transferred to the reaction vessel for hydrogenation.

The hydrogenation treatment may be conducted either with or without the presence of a catalyst. When conducting the nyd 'ogenation in the presence of a catalyst, a temperature within the range between about 0 C. and about 122.5 C. is employed, with a temperature between about 20 C. and about C. being preferred. Suitable operating pressures within the reaction vessel may be employed between about 1000 and about 5000 pounds per square inch, with pressures between about 1200 and about 2000 pounds per square inch being preferred for the optimum yield. of hydrazine. Suitable hydrogenation catalysts, are nickel, platinum, palladium, iron and their oxides, either supported or unsupported.

As indicated above, the hydrogenation treatment of the dimer may be conducted without the presence of a catalyst. Where non-catalytic hydrogenation of the dimer is to be employed, it is preferred that hydrogen employed in the treatment be generated in situ in an active state, rather than being introduced as molecular hydrogen. The evolution of active hydrogen in situ may be accomplished by reaction of a suitable metal or metal compound with a suitable acid or alkali. Forexample, metallic zinc or zinc dust may be reacted with acetic acid, in stoichiometric In conducting the above non-catalytic hydrogenation of the dimer to produce hydrazine, the dimer in the form of a suspension, as previously described, is added to the required amount of the metal or metallic compound (e. g., stannous chloride in Equation IV above). To this mixture the required amount of an acid is added (e. g., hydrochloric acid) to effect the evolution of active hydrogen and to produce a liquid mixture comprising hydrazine, gaseous alkane and other products of reaction. This hydrogenation treatment is conducted in a, suitable reaction vessel, at a temperature within the range between about 0 C. and about 50 0., with a temperature between about C. and about 25 C. being preferred.

As indicated above, the resulting mixture obtain-ed from either catalytic or non-catalytic hydrogenation of the dimer comprises a liquid mixture of hydrazine, gaseous alkane and other products of reaction. This mixture is next subjected to suitable phase separation to recover the alkane, as a gas phase, for further use or treatment in the process hereinbefore described. The remaining liquid phase, comprising a mixture of hydrazine and other reaction products, is next subjected to distillation to obtain hydrazine in the form of its hydrate as a product of the process.

For a fuller understanding of the process of the present invention, reference is had to the accompanying drawing which illustrates, diagrammatically, an elevational view of one form of the apparatus employed and capable of carrying out one embodiment of the process of the invention. It should be noted, however, that it is not intended that the invention be limited to the embodiment as illustrated but is capable of other embodiments which may extend beyond the scope of the apparatus illustrated. Some of the mechanical elements necessary to eifect the transfer of liquids and vapors and to maintain the conditions of temperature and pressure necessary to carry out the function of the apparatus, have been omitted to simplify the description.

Referring to the drawing, methane is introduced through conduit [0 into the upper end of a vertical quartz tube I I. This tube has a diameter of approximately 1 to 3 inches and a length of approximatel 50 inches. At a point approximately 2 to 4 inches below the introduction of methane through conduit I0, the methane is subjected to activation in activation zone 12 by photochemical radiation from a suitable source of ultra-violet light. Such light is transmitted through a quartz window l3 to effect activation of methane in the aforementioned activation zone in giving up the free methyl radical.

In order to effect reaction between the freed methyl radical and the aforementioned oxide of nitrogen, nitric oxide is introduced at a point along the quartz tube, through conduit M, approximately 6 to 15 inches below the point of introduction of methane. The resulting dimer is formed in zone l5. In order to maintain suitable temperatures within the tube during the above activation treatment of methane and subsequent dimer formation, the required temperature conditions are maintained within the tube by suitable heating or cooling means represented by heat exchanger 16.

The solid dimer reaction product in zone I5 is next withdrawn through valved-conduit l1, and transferred through this conduit into the upper portion of a separation vessel, represented by separation chamber !8. Separation chamber 18 is provided for effecting separation between gases and other products of reaction. For this purpose a suitable vehicle, such as hexane, is introduced into chamber it through a spray-valve I 9 positionedabove the entrance of conduit [1 into chamber l8. Hexane thus introduced into chamber 18 effects the cooling of the reaction product from zone 15 and forms a slurry so that gases may be separated out. These gases,-whi-ch may comprise methane, nitric oxide and nitrogen, are withdrawn through conduit 2e, while excess hexane, following settling action in chamber i8, is drawn off through conduit 2 l. The solid dimer, or dimer suspension, is withdrawn through valved-conduit 22 and transferred through this conduit to a suitable hydrogenation reactor 23.

In carrying out the hydrogenation treatment of the dimer to produce the desired hydrazine product, hydrogen is introduced at a point in the lower portion of reactor 23 through conduit 24. In order to maintain the desired temperature conditions within reactor 23 for hydrogenation, suitable heating means, represented by heat exchanger 25, are employed. The product of hydrogenation in hydrogenation zone 25 comprises a liquid mixture of hydrazine, gaseous alkane and other products of reaction. This mixture is Withdrawn from reactor 23 through conduit 21, and is subjected to further treatment in accordance with the process hereinbefore described to obtain hydrazine in the form of its hydrate as a product of the process.

Having thus described my invention, I claim:

1. A process for the manufacture of hydrazine which comprises: reacting an activated organic compound obtain-ed by the energization of a compound selected from the group consisting of methane, ethane, metal substituted methane and ethane, ethylene oxide and propylene oxide, in such manner as to contain a free alkyl radical of not more than two carbon atoms, with at least one oxide of nitrogen selected from the group consisting of nitric oxide and nitrogen trioxide at a temperature between about 20 C. and about 122.5 C. to produce a dimer of a nitrosoalkane; subjecting said dimer to hydro genatio-n at a temperature between about 0 C. and about 122.5 C. and at a pressure between about 1000 and about 5000 pounds per square inch to produce a mixture comprising hydrazine and an alkane; and separating hydrazine from said mixture.

2. A process for the manufacture of hydrazine which comprises: reacting an activated organic compound obtained by the energization of a cornpressure between about 1200 and. about 2000 pounds per square inch to produce a mixture comprising hydrazine and methane; and separating hydrazine from said mixture.

12. A process for the manufacture of a dimer of a nitrosoalkane which comprises: reacting an activated organic compound obtained by the energization of a compound selected from the group consisting of methane, ethane, metal substituted methane and ethane, ethylene oxide and propylene oxide, in such manner as to contain a free alkyl radical of not more than two carbon atoms, with at least one oxide of nitrogen selected from the group consisting of nitric oxide and nitrogen trioxide at a temperature between about 20 C. and about 122.5 C. to produce a dimer of a nitrosoalkane.

13. A process for the manufacture of a dimer of a nitrosoalkane which comprises: reacting an activated organic compound obtained by the energization of a compound selected from the group consisting of methane, ethane, metal substituted methane and ethane, ethylene oxide and propylene oxide, in such manner as to contain a free alkyl radical of not more than two carbon atoms, with at least one oxide of nitrogen selected from the group consisting of nitric oxide and nitrogen trioxide at a temperature between about 20 C. and about 20 C. to produce a dimer of a nitrosoalkane.

14. A process for the manufacture of the dimer of nitrosomethane which comprises: reacting activated methane, obtained by the energization of methane in such manner as to contain a free methyl radical, with nitric oxide at a temperature between about -20 C. and about 122.5 C. to produce the dimer of nitrosomethane.

15. A process for the manufacture of the dimer of nitrosoethane which comprises: reacting activated ethane, obtained by the energization of ethane in such manner as to contain a free ethyl radical, with nitric oxide at a temperature between about 20 C. and about 122.5 C. to produce the dimer of nitrosoethane.

16. A process for the manufacture of the dimer of nitrosomethane which comprises: reacting an activated metal-substituted methane, obtained by the energization of a metal-substituted methane in such manner as to contain a free methyl radical, with nitric oxide at a temperature between about -20 C. and about 122.5 C. to produce the dimer of nitrosomethane.

17. A process for the manufacture of the dimer of nitrosoethane which comprises: reacting an activated metal-substituted ethane, obtained by the energization of a metal-substituted ethane in such manner as to contain a free ethyl radical, with nitric oxide at a temperature between about -20 C. and about 122.5 C- to produce the dimer of nitrosoethane.

18. A process for the manufacture of the dimer of nitrosomethane which comprises: reacting activated ethylene oxide, obtained by the energization of ethylene oxide in such manner as to contain a free methyl radical, with nitric oxide at a temperature between about -20 C. and about 122.5 C. to produce the dimer of nitrosomethane.

References Cited in the file of this patent Degering: "An Outline of Organic Nitrogen Compounds, 1945 ed., page 110. University 

1. A PROCESS FOR THE MANUFACTURE OF HYDRAZINE WHICH COMPRISES: REACTING AN ACTIVATED ORGANIC COMPOUND OBTAINED BY THE ENERGIZATION OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF METHANE, ETHANE, METAL SUBSTITUTED METHANE AND ETHANE, ETHYLENE OXIDE AND PROPYLENE OXIDE, IN SUCH MANNER AS TO CONTAIN A "FREE" ALKYL ARADICAL OF NOT MORE THAN TWO CARBON ATOMS, WITH AT LEAST ONE OXIDE OF NITRIC SELECTED FROM THE GROUP CONSISTING OF NITRIC OXIDE AND NITROGEN TRIOXIDE AT A TEMPERATURE BETWEEN ABOUT -20* C. AND ABOUT 122.5* C. TO PRODUCE A DIMER OF A NITROSOALKANE; SUBJECTING SAID DIMER TO HYDROGENATION AT A TEMPERATURE BETWEEN ABOUT 0* C. AND ABOUT 122.5* C. AND AT A PRESSURE BETWEEN ABOUT 1000 AND ABOUT 5000 POUNDS PER SQUARE INCH TO PRODUCE A MIXTURE COMPRISING HYDRAZINE AND AN ALKANE; AND SEPARATING HYDRAZINE FROM SAID MIXTURE. 